Construction method of drilling and connecting pipes in reinforced concrete pool without water stopping

Abstract

The present invention discloses a method for drilling and pipe-taking construction without water shutoff in a reinforced concrete pool, and the process flow is steel cofferdam production → steel cofferdam installation → earth excavation → pool wall milling → pipeline installation → gate installation → water-tightening test → steel cofferdam removal. Compared with the construction process of a newly built auxiliary concrete structure well, the special steel cofferdam designed by the present invention has the following advantages: construction personnel do not need to work in the pool, ensuring safety; after drilling holes in the pool wall, waterproof and anti-corrosion construction of cut steel bars can be done to ensure the long-term safety of the structure; there is no construction and maintenance period for concrete structure wells, the construction period is short, the economic investment is small, and the environmental impact is small; the present invention calculates the acting force before installing the steel cofferdam, and adopts an appropriate fixed structure to ensure that the manufactured steel cofferdam can withstand the water pressure of the pool water without deformation and damage, while overcoming the influence of buoyancy on the floating of the steel cofferdam, ensuring the safe implementation of the construction process such as drilling and pipe-taking.

Description

Technical Field

[0001] The invention relates to the technical field of drainage reconstruction, and in particular to a construction method for drilling and connecting pipes in a reinforced concrete pool without water stopping. Background Art

[0002] During the upgrading and transformation of sewage treatment plants, ensuring the normal operation of the original water treatment process without water cut-off during construction is a common problem; especially difficult is the construction of drilling holes and connecting pipes without water cut-off on the wall of a reinforced concrete pool that is full of water.

[0003] The present invention attempts to apply a construction process of a steel cofferdam with holes in the wall of a reinforced concrete pool without water shutoff in a sewage treatment plant expansion and renovation project, and conducts systematic analysis and research, so as to provide reliable experience for similar construction operations in the future. Summary of the invention

[0004] The purpose of the present invention is to solve the shortcomings of the prior art and to propose a construction method for drilling holes and taking up pipes in a reinforced concrete water pool without water shutoff.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] The construction method of drilling and connecting pipes for reinforced concrete pool without water stopping includes the following steps:

[0007] Steel cofferdam design dimensions The main frame is made of 10# channel steel and the weir wall is made of The steel plate is reinforced with 5# angle steel, and a 30mm thick rubber-plastic strip is used between the steel cofferdam and the concrete pool body for water-blocking and sealing;

[0008] Use a submersible pump to pump out the water in the cofferdam multiple times, and use it every time the water level drops. Hot-dip galvanized expansion bolts fix the steel cofferdam to the concrete pool wall;

[0009] Finally, all the water in the steel cofferdam is pumped out, forming an independent water-free space;

[0010] Then, after accurate positioning from the outside of the pool body, a φ100 water drill is used to complete the drilling operation on the concrete pool wall. After the relevant pipes and gates are installed, the steel cofferdam is removed to complete the construction of the entire renovation project.

[0011] Furthermore, the above-mentioned reinforced concrete pool non-stop water opening and pipe connection construction method specifically includes the following steps:

[0012] S1. Steel cofferdam production:

[0013] Steel cofferdams were made according to the depth and width of the pool. The total depth of the modified pool structure was 5.7m. The liquid level in the pool was measured on site. ;Steel cofferdam structure dimensions , that is, a=2m, b=0.8m, h 1 =5m, deadweight m=1429kg, hung on the top of the concrete pool; after the steel cofferdam is installed, the maximum liquid level depth in the cofferdam is h=5m-1m=4m;

[0014] S2. Stress analysis of steel cofferdam:

[0015] The key difficulty in the implementation of the present invention is the production and installation of the steel cofferdam, and the stress analysis of the steel cofferdam is the top priority of the entire work: we need to ensure that the manufactured steel cofferdam can withstand the water pressure of the pool water without deformation and damage, and at the same time overcome the influence of buoyancy on the floating of the steel cofferdam;

[0016] According to the pool size and the installation position of the steel cofferdam, the force of water pressure and buoyancy on the steel cofferdam after installation is estimated, including the following aspects:

[0017] 1) Verification and analysis of water pressure acting on steel cofferdam

[0018] ① Force analysis of the main water-facing surface of the steel cofferdam

[0019] The height of the steel cofferdam immersed in water is h=4m;

[0020] Force area of ​​main water-facing surface of steel cofferdam ;

[0021] Centroid location ;

[0022] Moment of inertia ;

[0023] Assume that the total hydrostatic pressure acting on the main water-facing steel cofferdam is Fp, then

[0024] ;

[0025] ——where h C is the depth of the centroid C of the compression plane below the free surface,

[0026] The direction of the total hydrostatic pressure is perpendicular to the plane of the steel cofferdam and points to the steel cofferdam;

[0027] The distance of the pressure center D from the free surface ;

[0028] ②Analysis of the force on the water-facing surface of the steel cofferdam

[0029] The height of the steel cofferdam immersed in water is h=4m;

[0030] Force area of ​​the water-facing surface of the steel cofferdam ;

[0031] Centroid location ;

[0032] Moment of inertia ;

[0033] Assume that the total hydrostatic pressure acting on the steel cofferdam on the water-facing side is ,but

[0034] ;

[0035] ——In the formula The centroid of the compression plane The depth below the free surface,

[0036] The direction of the total hydrostatic pressure is perpendicular to the plane of the steel cofferdam and points to the steel cofferdam;

[0037] Pressure Center Position from the free surface

[0038] ;

[0039] ③Stress analysis of steel cofferdam bottom surface

[0040] The bottom surface of the steel cofferdam is mainly affected by the upward buoyancy and its own gravity. The maximum buoyancy of the steel cofferdam is set to , the weight of the steel cofferdam itself is , through calculation we can get:

[0041]

[0042] ,

[0043] ,

[0044] The force on the bottom of the steel cofferdam is ,but

[0045] ;

[0046] 2) Analysis and verification of buoyancy force on steel cofferdam

[0047] From the above steel cofferdam bottom force analysis and calculation process, we can know that:

[0048]

[0049] ,

[0050] ,

[0051] From the above calculations, we can see that , without considering the influence of friction and water pressure in the pool, it is necessary to take fixing measures to prevent the steel cofferdam from floating when pumping water in the steel cofferdam;

[0052] The condition for the steel cofferdam to start floating is that the gravity of the water pumped out of the steel cofferdam is greater than the dead weight of the steel cofferdam, and the water level is set to drop to △h pump; then:

[0053] ,

[0054] From this, the maximum safe water level drop in the first steel cofferdam can be obtained:

[0055]

[0056] ,

[0057] After all the water in the steel cofferdam is removed, the maximum upward force on the steel cofferdam is ,but:

[0058] ,

[0059] Using 4.8 level Galvanized expansion bolts are used to fix steel cofferdams. Check the product manual to find out that: The allowable shear force of galvanized bolts is ,

[0060] The number of expansion bolts required can be obtained from this , take the integer and you will know that at least 7 M12 galvanized expansion bolts are needed for fixing;

[0061] S3. Steel cofferdam installation:

[0062] Use a crane to hoist the steel cofferdam. First, slowly and safely hoist the steel cofferdam to the location to be installed in the pool, and then use a submersible pump to pump out the water in the cofferdam. When the steel cofferdam is not fixed with expansion bolts for the first time, the maximum safe water level drops to 0.89m, and at least There are 7 galvanized expansion bolts. The total depth of the liquid level in the weir is 4m. To ensure safety, the installation plan of multiple pumping and timely fixing is adopted.

[0063] S4, milling holes in concrete pool wall:

[0064] After the steel cofferdam successfully isolates the pool wall from the pool water, the concrete pool wall drilling operation can begin. A φ100 water drill is used for milling holes, and the hole position should be accurately located before milling holes;

[0065] S5, Gate and pipeline installation:

[0066] After the milling is completed, the gate and pipeline are installed. To prevent leakage between the pool wall holes and the pipeline, the outer wall of the pipeline is welded with a water stop ring, the pipeline is butt welded inside and outside, anti-corrosion is done, and the holes are sealed with grouting material; the gate frame is fixed to the concrete pool wall with chemical bolts, and the formwork is poured with grouting material, and the verticality of the gate installation must be ensured;

[0067] S6. Steel cofferdam removal:

[0068] After the closed water test is passed to ensure that the gate leakage meets the requirements, the dismantling of the steel cofferdam begins. The dismantling steps are the opposite of the installation steps.

[0069] Preferably, the S1 steel cofferdam production also includes the following matters needing attention:

[0070] 1) It is necessary to make welded steel cofferdams according to the stress analysis and verification results of steel cofferdams, and reinforce the main stress-bearing parts;

[0071] 2) Welders of steel cofferdams must be certified to ensure welding quality;

[0072] 3) When pasting rubber-plastic waterproof strips, the contact surface must be rust-free and strong adhesive must be used to prevent the formation of a path due to water pressure.

[0073] Preferably, the S3 steel cofferdam installation solution includes the following steps:

[0074] 1) When the liquid level drops by 0.52m for the first time, stop pumping water and install 3 Galvanized expansion bolts are used for fixing;

[0075] 2) When the second liquid level drops by 0.9m, stop pumping water and install two Galvanized expansion bolts are used for fixing. At this time, 10 Galvanized expansion bolts are used to fix the steel cofferdam to eliminate the influence of the maximum buoyancy on the floating of the steel cofferdam;

[0076] 3) When the water level drops by 2.8m, stop pumping and install 3 Galvanized expansion bolts are used for fixing. At this time, 8 bolts are used on each side of the steel cofferdam, for a total of 16 bolts Galvanized expansion bolts are used for fixing, which fully meets the safety requirements for the use of steel cofferdams;

[0077] 4) Continue pumping until the remaining water in the steel cofferdam is pumped out, and observe the sealing condition between the steel cofferdam and the concrete pool wall.

[0078] Furthermore, after the installation of the steel cofferdam is completed, in order to ensure absolute safety, the steel cofferdam must be observed for at least 24 hours to check for deformation and water seepage and leakage under the action of water pressure. If there is no deformation and water seepage exceeds the pumping capacity of the water pump, the construction of the subsequent process can be started.

[0079] Preferably, the S6 steel cofferdam removal comprises the following steps:

[0080] 1) Fill the cofferdam with water until the liquid level drops to 2.8m, and remove the three expansion bolts at the bottom of both sides of the cofferdam;

[0081] 2) Continue to inject water into the cofferdam until the liquid level drops to 0.9m, and remove the two expansion bolts at the bottom of both sides of the cofferdam;

[0082] 3) Continue to inject water into the cofferdam until the liquid level drops by 0.5m, and remove all the remaining 3 expansion bolts on both sides of the cofferdam;

[0083] 4) Use a crane to slowly install and lift the steel cofferdam out of the pool to complete the demolition work.

[0084] Compared with the prior art, the present invention has the following beneficial effects:

[0085] 1. Compared with the construction process of newly built auxiliary concrete structure wells, the special steel cofferdam designed by the present invention has the following advantages: construction workers do not need to work in the pool, ensuring safety; after the pool wall is opened, waterproof and anti-corrosion construction of cut steel bars can be carried out to ensure the long-term safety of the structure; there is no construction and maintenance period of the concrete structure well, the construction period is short, the economic investment is small, and the environmental impact is small.

[0086] 2. Based on reasonable theoretical calculations, the present invention adopts an appropriate fixed structure to ensure that the manufactured steel cofferdam can withstand the water pressure of the pool water without deformation or damage, while overcoming the influence of buoyancy on the floating of the steel cofferdam, ensuring the safe implementation of construction processes such as opening holes and taking over pipes.

[0087] 3. To summarize, the process of the present invention is: steel cofferdam production → steel cofferdam installation → earth excavation → pool wall milling → pipeline installation → gate installation → water-tightness test → steel cofferdam removal, and force calculation is performed before installation. Theoretical calculations and actual construction results show that the special steel cofferdam is safe and reliable in the hole opening operation on the wall of a full water concrete pool, has good economic benefits, and has little impact on the water body and the environment. It is currently the optimal process for the non-stop water opening and reconstruction construction of the reinforced concrete pool wall. BRIEF DESCRIPTION OF THE DRAWINGS

[0088] Figure 1 A schematic diagram of the force analysis of the main water-facing surface of the steel cofferdam in the non-water-stopping drilling and pipe-connecting construction method for a reinforced concrete pool proposed by the present invention;

[0089] Figure 2This is a schematic diagram of the force analysis of the water-facing surface of the steel cofferdam in the non-water-stopping drilling and pipe connection construction method for a reinforced concrete pool proposed by the present invention. DETAILED DESCRIPTION

[0090] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0091] 1. Project Introduction

[0092] The first phase of the Hongjiang Drainage Expansion and Reconstruction Project - the fourth phase of the Hongjiang Drainage Standard Improvement and Reconstruction Project is located in the existing filter cloth filter and the east side of the chlorination contact tank in the factory area of ​​Hongjiang Drainage Co., Ltd. In order to divert the effluent from the chlorination contact tank to the newly built artificial wetland, it is necessary to drill a hole in the concrete tank body (wall thickness 500mm) on the east side of the chlorination contact tank to build a new DN1200 welded steel pipe (the pipe has been connected to the east side of the chlorination contact tank), and at the same time install a set of Φ1200 hand-held and electric dual-purpose copper-inlaid cast iron round gates on the inner side of the chlorination contact tank wall.

[0093] The current discharge capacity of the chlorination contact pool outlet is 225,000 m³ / d, and there is no bypass pipeline. Therefore, water cannot be stopped for construction during the renovation process, which brings great difficulties to the renovation project. How to effectively separate the large amount of water in the concrete pool from the pool wall is the key to the smooth progress of this renovation project.

[0094] 2. Analysis of the advantages and disadvantages of traditional construction technology and the special steel cofferdam construction of this project

[0095] 2.1 Conventional water-blocking cofferdams in hydraulic projects

[0096] The conventional water-blocking cofferdam types for water conservancy projects include earth-rock cofferdam, grass-soil cofferdam, wooden pile cofferdam, wooden cage cofferdam, steel sheet pile cofferdam, locking pipe pile cofferdam, reinforced concrete cofferdam, etc.

[0097] This project needs to block water inside the existing concrete water pool (the single-cell concrete water pool in the operation area is 36.8m long, 2.5m wide, 5.5m deep, and has an inflow of 225,000 m3 / d). The original pool body must not be damaged. At the same time, the incoming water quality has been treated to meet the standards and can be discharged directly. The construction work must not cause secondary pollution. Therefore, conventional water-blocking cofferdams are not suitable for use in this project in terms of process matching and economic benefits.

[0098] 2.2 New auxiliary concrete structure well outside the pool

[0099] When the concrete pool is transformed and connected without water cut-off, it is also a common construction process to add an auxiliary concrete structural well. This construction process uses the original concrete pool wall as one side of the well wall of the new structural well, implants steel bars at the corresponding position of the pool wall, casts the bottom of the structural well and the other three sides of the well wall, and after the discharge pipe and the corresponding control gate (installed on the side of the original pool body) are installed, a hole is opened on the existing concrete pool wall (i.e., first install a steel cable fixing ring with expansion bolts on the concrete pool wall to be opened, firmly connect one end of the steel wire rope to the fixing ring, and fix the other end outside the structural well; then use a φ100 water drill to drill the original concrete pool wall along the hole contour line to 9 / 10 of the depth, and after the drilled holes are connected, use a long crowbar to pry off and remove the concrete block), thereby completing the hole opening operation on the water cut-off pool wall.

[0100] This construction process will cause the drilling depth to be too deep, which may easily lead to water seepage from the pool wall during the drilling process and make subsequent operations difficult to carry out; if the drilling depth is too shallow, it may easily lead to difficulty in prying off the concrete block; after the concrete block is pried off, the water in the pool will flood the hole, and it will be impossible to perform waterproofing and anti-corrosion operations on the pool wall after the hole is opened. Long-term operation will inevitably cause corrosion of the steel bars, affecting the safety of the structure; it is not suitable for use in pools with high water levels; adding a structural well requires a large economic investment, and at the same time it is not in harmony with the surrounding environment and affects the appearance.

[0101] 2.3 Special steel cofferdam for this project

[0102] In view of the requirements of this project that the concrete pool structure cannot be damaged, the pool water cannot be polluted again, and the surrounding environment outside the pool does not affect the appearance due to renovation, a special steel cofferdam is used.

[0103] Steel cofferdam design dimensions The main frame is made of 10# channel steel and the weir wall is made of The steel plate is reinforced with 5# angle steel, and a 30mm thick rubber-plastic strip is used between the steel cofferdam and the concrete pool body for water-blocking sealing; a submersible pump is used to pump out the water in the cofferdam multiple times, and the water level is used every time it drops. Hot-dip galvanized expansion bolts are used to fix the steel cofferdam to the concrete pool wall. Finally, all the water in the steel cofferdam is pumped out to form an independent water-free space. Then, after accurate positioning from the outside of the pool body, a φ100 water drill is used to complete the hole drilling operation on the concrete pool wall. After the relevant pipes and gates are installed, the steel cofferdam is dismantled to complete the construction of the entire renovation project.

[0104] Compared with the construction technology of newly built auxiliary concrete structure wells, the construction workers of the special steel cofferdam do not need to work in the pool, which ensures safety; after the holes in the pool wall are opened, waterproof and anti-corrosion construction of the cut steel bars can be carried out to ensure the long-term safety of the structure; there is no construction and maintenance period of the concrete structure well, the construction period is short, the economic investment is small, and the environmental impact is small.

[0105] 3. Stress analysis of steel cofferdam

[0106] The key and difficult points in the implementation of this project are the production and installation of the steel cofferdam, and the stress analysis of the steel cofferdam is the top priority of the entire work: we need to ensure that the steel cofferdam can withstand the water pressure of the pool water without deformation and damage, and at the same time overcome the impact of buoyancy on the floating of the steel cofferdam.

[0107] The total depth of the modified pool structure is 5.7m, and the liquid level in the pool is measured on site. ;Steel cofferdam structure dimensions , that is, a=2m, b=0.8m, h 1 =5m, deadweight m=1429kg, hung on the top of the concrete pool; after the steel cofferdam is installed, the maximum liquid level depth in the cofferdam is h=5m-1m=4m.

[0108] 3.1 Analysis of the force of water pressure on steel cofferdam

[0109] 3.1.1 Force analysis of the main water-facing surface of the steel cofferdam

[0110] Reference Figure 1 , the height of the steel cofferdam immersed in water is h=4m;

[0111] Force area of ​​main water-facing surface of steel cofferdam ;

[0112] Centroid location ;

[0113] Moment of inertia ;

[0114] Assume that the total hydrostatic pressure acting on the main water-facing steel cofferdam is Fp, then

[0115] ;

[0116] ——where h C is the depth of the centroid C of the compression plane below the free surface

[0117] The direction of the total hydrostatic pressure is perpendicular to the plane of the steel cofferdam and points to the steel cofferdam.

[0118] The distance of the pressure center D from the free surface

[0119] .

[0120] 3.1.2 Force analysis on the water-facing surface of the steel cofferdam

[0121] Reference Figure 2 Schematic diagram of force analysis on the water-facing surface of the steel cofferdam:

[0122] The height of the steel cofferdam immersed in water is h=4m;

[0123] Force area of ​​the water-facing surface of the steel cofferdam ;

[0124] Centroid location ;

[0125] Moment of inertia ;

[0126] Assume that the total hydrostatic pressure acting on the steel cofferdam on the water-facing side is ,but

[0127] ;

[0128] ——In the formula The centroid of the compression plane Depth below the free surface

[0129] The direction of the total hydrostatic pressure is perpendicular to the plane of the steel cofferdam and points to the steel cofferdam.

[0130] Pressure Center Position from the free surface

[0131] .

[0132] 3.1.3 Stress analysis of steel cofferdam bottom surface

[0133] The bottom surface of the steel cofferdam is mainly affected by the upward buoyancy and its own gravity. The maximum buoyancy of the steel cofferdam is set to , the weight of the steel cofferdam itself is , through calculation we can get:

[0134]

[0135] ,

[0136] ,

[0137] The force on the bottom of the steel cofferdam is ,but

[0138] .

[0139] 3.2 Analysis of buoyancy force on steel cofferdam

[0140] From the above 3.1.1 steel cofferdam bottom surface force analysis calculation process, we can know that

[0141]

[0142] ,

[0143] ,

[0144] From the above calculations, we can see that Without considering the influence of friction and water pressure in the pool, fixed measures must be taken to prevent the steel cofferdam from floating when pumping water inside the steel cofferdam.

[0145] The condition for the steel cofferdam to start floating is that the gravity of the water pumped out of the steel cofferdam is greater than the dead weight of the steel cofferdam, and the water level is set to drop to △h pump; then:

[0146]

[0147] The maximum safe water level drop in the first steel cofferdam can be obtained.

[0148]

[0149] ,

[0150] After all the water in the steel cofferdam is removed, the maximum upward force on the steel cofferdam is ,but:

[0151] ,

[0152] This project uses 4.8 Galvanized expansion bolts are used to fix steel cofferdams. According to the relevant manual, The allowable shear force of galvanized bolts is ,

[0153] The number of expansion bolts required can be obtained from this , take the integer and you will know that at least 7 M12 galvanized expansion bolts are needed for fixing.

[0154] 4. Construction steps of opening and connecting pipe without water stopping

[0155] 4.1 Process flow

[0156] Steel cofferdam production → Steel cofferdam installation → Earth excavation → Pool wall milling hole → Pipeline installation → Gate installation → Water closure test → Steel cofferdam removal

[0157] 4.2 Operation points

[0158] 4.2.1 Steel cofferdam production

[0159] (1) It is necessary to manufacture welded steel cofferdams based on the stress analysis and verification results of the steel cofferdams, and to reinforce the main stress-bearing parts;

[0160] (2) Welders of steel cofferdams must be certified to ensure welding quality;

[0161] (3) When pasting rubber-plastic waterproof strips, the contact surface must be rust-free and strong adhesive must be used to prevent the formation of a path due to water pressure.

[0162] 4.2.2 Steel cofferdam installation

[0163] Use a crane to hoist the steel cofferdam. First, slowly and safely hoist the steel cofferdam to the location to be installed in the pool, and then use a submersible pump to pump out the water in the cofferdam. From the chapter "3.2 Analysis of the force verification of buoyancy on the steel cofferdam", it can be seen that when the steel cofferdam is not fixed with expansion bolts for the first time, the maximum safe water level drops to 0.89m, and at least The number of galvanized expansion bolts is 7.

[0164] The total depth of the liquid level in the weir is 4m. In order to ensure safety, the installation plan of multiple pumping and timely fixing is adopted:

[0165] 1) When the liquid level drops by 0.52m for the first time, stop pumping water and install 3 Galvanized expansion bolts are used for fixing;

[0166] 2) When the second liquid level drops by 0.9m, stop pumping water and install two Galvanized expansion bolts are used for fixing. At this time, 10 Galvanized expansion bolts are used to fix the steel cofferdam to eliminate the influence of the maximum buoyancy on the floating of the steel cofferdam;

[0167] 3) When the water level drops by 2.8m, stop pumping and install 3 Galvanized expansion bolts are used for fixing. At this time, 8 bolts are used on each side of the steel cofferdam, for a total of 16 bolts Galvanized expansion bolts are used for fixing, which fully meets the safety requirements for the use of steel cofferdams;

[0168] 4) Continue pumping until the remaining water in the steel cofferdam is pumped out, and observe the sealing condition between the steel cofferdam and the concrete pool wall.

[0169] At this point, the installation of the steel cofferdam has been completed. In order to ensure safety, the steel cofferdam must be observed for at least 24 hours to check for deformation and water seepage and leakage under the action of water pressure. If there is no deformation and water seepage exceeds the pumping capacity of the water pump, the subsequent construction process can be started.

[0170] 4.2.3 Milling holes in concrete pool wall

[0171] After the steel cofferdam successfully isolates the pool wall from the pool water, the concrete pool wall drilling operation can begin. Use a φ100 water drill for milling holes, and the hole position should be accurately located before milling.

[0172] 4.2.4 Gate and pipeline installation

[0173] After the milling is completed, the gate and pipeline are installed. In order to prevent leakage between the holes in the pool wall and the pipeline, a water stop wing ring is welded to the outer wall of the pipeline, the pipeline is welded inside and outside, anti-corrosion is done, and grouting material is used to seal the holes; the gate frame is fixed to the concrete pool wall with chemical bolts, and the formwork is poured with grouting material to ensure the verticality of the gate installation.

[0174] 4.2.5 Removal of steel cofferdam

[0175] After the closed water test is passed to ensure that the gate leakage meets the requirements, the removal of the steel cofferdam begins; the removal steps are opposite to the installation steps, namely:

[0176] 1) Fill the cofferdam with water until the liquid level drops to 2.8m, and remove the three expansion bolts at the bottom of both sides of the cofferdam;

[0177] 2) Continue to inject water into the cofferdam until the liquid level drops to 0.9m, and remove the two expansion bolts at the bottom of both sides of the cofferdam;

[0178] 3) Continue to inject water into the cofferdam until the liquid level drops by 0.5m, and remove all the remaining 3 expansion bolts on both sides of the cofferdam;

[0179] 4) Use a crane to slowly install and lift the steel cofferdam out of the pool to complete the demolition work.

[0180] 5. Conclusion

[0181] Theoretical calculations and actual construction results have shown that special steel cofferdams are safe and reliable in drilling holes in the walls of full concrete pools, have good economic benefits, and have little impact on water bodies and the environment. They are currently the optimal technology for drilling holes in the walls of reinforced concrete pools without stopping water.

[0182] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for drilling and connecting pipes in reinforced concrete pools without water shutoff, characterized in that: The following steps are involved: S1. Steel cofferdam production: Steel cofferdams were made according to the depth and width of the pool. The total depth of the modified pool structure was 5.7m. The liquid level in the pool was measured on site. ; Steel cofferdam structure dimensions , that is, a=2m, b=0.8m, h1=5m, deadweight m=1429kg, hung on the top of the concrete pool; After the steel cofferdam is installed, the maximum liquid level depth in the cofferdam is h=5m-1m=4m; S2. Stress analysis of steel cofferdam: According to the pool size and the installation position of the steel cofferdam, the force of water pressure and buoyancy on the steel cofferdam after installation is estimated, including the following aspects: 1) Verification and analysis of water pressure acting on steel cofferdam ① Force analysis of the main water-facing surface of the steel cofferdam The height of the steel cofferdam immersed in water is h=4m; Force area of ​​main water-facing surface of steel cofferdam ; Centroid location ; Moment of inertia ; Assume that the total hydrostatic pressure acting on the main water-facing steel cofferdam is Fp, then ； ——where h C is the depth of the centroid C of the compression plane below the free surface, The direction of the total hydrostatic pressure is perpendicular to the plane of the steel cofferdam and points to the steel cofferdam; The distance of the pressure center D from the free surface ； ②Analysis of the force on the water-facing surface of the steel cofferdam The height of the steel cofferdam immersed in water is h=4m; Force area of ​​the water-facing surface of the steel cofferdam ; Centroid location ; Moment of inertia ; Assume that the total hydrostatic pressure acting on the steel cofferdam on the water-facing side is ,but ； ——In the formula The centroid of the compression plane The depth below the free surface, The direction of the total hydrostatic pressure is perpendicular to the plane of the steel cofferdam and points to the steel cofferdam; Pressure Center Position from the free surface ； ③Stress analysis of steel cofferdam bottom surface The bottom surface of the steel cofferdam is mainly affected by the upward buoyancy and its own gravity. The maximum buoyancy of the steel cofferdam is set to , the weight of the steel cofferdam itself is , through calculation we can get: ， ， The force on the bottom of the steel cofferdam is ,but ； 2) Analysis and verification of buoyancy force on steel cofferdam From the above steel cofferdam bottom force analysis and calculation process, we can know that: ， ， From the above calculations, we can see that , without considering the influence of friction and water pressure in the pool, it is necessary to take fixing measures to prevent the steel cofferdam from floating when pumping water in the steel cofferdam; The condition for the steel cofferdam to start floating is that the gravity of the water pumped out of the steel cofferdam is greater than the dead weight of the steel cofferdam, and the water level is set to drop to △h pump; then: From this, the maximum safe water level drop in the first steel cofferdam can be obtained: ， After all the water in the steel cofferdam is removed, the maximum upward force on the steel cofferdam is ,but: ， Using 4.8 level Galvanized expansion bolts are used to fix steel cofferdams. Check the product manual to find out that: The allowable shear force of galvanized bolts is , The number of expansion bolts required can be obtained from this , take the integer and you will know that at least 7 M12 galvanized expansion bolts are needed for fixing; S3. Steel cofferdam installation: Use a crane to hoist the steel cofferdam. First, slowly and safely hoist the steel cofferdam to the location to be installed in the pool, and then use a submersible pump to pump out the water in the cofferdam. When the steel cofferdam is not fixed with expansion bolts for the first time, the maximum safe water level drops to 0.89m, and at least There are 7 galvanized expansion bolts. The total depth of the liquid level in the weir is 4m. To ensure safety, the installation plan of multiple pumping and timely fixing is adopted. The S3 steel cofferdam installation scheme includes the following steps: 1) When the liquid level drops by 0.52m for the first time, stop pumping water and install 3 Galvanized expansion bolts are used for fixing; 2) When the second liquid level drops by 0.9m, stop pumping water and install two Galvanized expansion bolts are used for fixing. At this time, 10 Galvanized expansion bolts are used to fix the steel cofferdam to eliminate the influence of the maximum buoyancy on the floating of the steel cofferdam; 3) When the water level drops by 2.8m, stop pumping and install 3 Galvanized expansion bolts are used for fixing. At this time, 8 bolts are used on each side of the steel cofferdam, for a total of 16 bolts Galvanized expansion bolts are used for fixing, which fully meets the safety requirements for the use of steel cofferdams; 4) Continue pumping until the remaining water in the steel cofferdam is completely pumped out, and observe the sealing condition between the steel cofferdam and the concrete pool wall; S4, milling holes in concrete pool wall: After the steel cofferdam successfully isolates the pool wall from the pool water, the concrete pool wall drilling operation can begin. A φ100 water drill is used for milling holes, and the hole position should be accurately located before milling holes; S5, Gate and pipeline installation: After the milling is completed, the gate and pipeline are installed. To prevent leakage between the pool wall holes and the pipeline, the outer wall of the pipeline is welded with a water stop ring, the pipeline is butt welded inside and outside, anti-corrosion is done, and the holes are sealed with grouting material; the gate frame is fixed to the concrete pool wall with chemical bolts, and the formwork is poured with grouting material, and the verticality of the gate installation must be ensured; S6. Steel cofferdam removal: After the closed water test is passed to ensure that the gate leakage meets the requirements, the removal of the steel cofferdam will begin; The S6 steel cofferdam removal includes the following steps: 1) Fill the cofferdam with water until the liquid level drops to 2.8m, and remove the three expansion bolts at the bottom of both sides of the cofferdam; 2) Continue to inject water into the cofferdam until the liquid level drops to 0.9m, and remove the two expansion bolts at the bottom of both sides of the cofferdam; 3) Continue to inject water into the cofferdam until the liquid level drops by 0.5m, and remove all the remaining 3 expansion bolts on both sides of the cofferdam; 4) Use a crane to slowly install and lift the steel cofferdam out of the pool to complete the demolition work.

2. The method for constructing reinforced concrete pools without water shutoff according to claim 1, characterized in that: The S1 steel cofferdam production also includes the following matters needing attention: 1) It is necessary to make welded steel cofferdams according to the stress analysis and verification results of steel cofferdams, and reinforce the main stress-bearing parts; 2) Welders of steel cofferdams must be certified to ensure welding quality; 3) When pasting rubber-plastic waterproof strips, the contact surface must be rust-free and strong adhesive must be used to prevent the formation of a path due to water pressure.

3. The method for constructing reinforced concrete pools without water shutoff according to claim 1, characterized in that: After the installation of the steel cofferdam is completed, in order to ensure safety, the steel cofferdam must be observed for at least 24 hours to check the deformation and water seepage and leakage under the action of water pressure. If there is no deformation and water seepage exceeds the pumping capacity of the water pump, the construction of the subsequent process can be started.

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